This paper contains the results of laboratory and field tests where the corrosion system was carbon steel exposed to oilfield brines containing dissolved carbon dioxide and oxygen. Both uninhibited and inhibited systems were examined. The results are analyzed and placed in context with previously reported work dealing with related systems.

Oilfields, in general, have less gas pressure as they mature. Ingress of oxygen into well annuli, into the vapor space in tanks, and through pump packing becomes more commonplace as a result. The corrosion consequences of this condition can now be quantified and corrective action can be taken to avoid equipment replacement and production losses.

To the author’s knowledge, no report of a systematic treatment of this subject exists in corrosion literature. Quantification of the effects, recognition of duration, and influence of corrosion inhibitor chemical types are among the novel contributions of this paper.

Some of the significant conclusions from the work concern the magnitude and persistency of corrosion acceleration by oxygen in sweet fluids. At common oil well temperatures, acceleration was in the order of 10 to 30 mpy per part per million of oxygen. The concentration of oxygen was not reduced preferentially from these solutions but occurred at approximately the same rate as reduction of dissolved carbon dioxide (undissociated carbonic acid) concentration. Inhibition of corrosion in CO2/O2 systems was more difficult that in CO2 alone but could be accomplished.

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